Question UPS: When to enter Safe Mode?

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Question UPS: When to enter Safe Mode?


NAS Support
DS1520+, DS218+, DS215j
  1. RT2600ac
  2. MR2200ac
  3. RT6600ax
  4. WRX560
Operating system
  1. macOS
Mobile operating system
  1. iOS
With three smallish APC UPS I decided to re-configure what's connected to each one. The two DSM NAS are to the same UPS so that one monitors and the other shares the status. Up to now I had kept the Safe Mode entry on 'Until low battery' thinking that is would be fairly low but able to withstand a second or even third power 'bounce' and still keep the NAS disks safe. Also with setting 'shutdown UPS on entering safe mode' and reboot after power outage.

I wasn't prepared that safe mode would be entered somewhere around 60-62% of battery remaining: I wasn't overly monitoring this as I was test it and a smaller/older UPS by switching off the wall socket and the NAS's UPS is bigger with and had ages to run.

Question 1: Is better to manually set a 'run for XX minutes before safe mode' to get a longer initial run on battery or stick with a 60% power down?

On my Mac the settings allow for shutdown when the battery has X minutes and/or Y% remaining. It seems a more obvious way to set this rather than hoping the UPS can run for XX minutes.

Question 2: And why doesn't SRM have any UPS configuration?
Now I have set minutes. Tested 2x per year.

Regarding the "Until low battery" - it's tricky.
Some vendors in their low end UPS have setup of interval before UPS shutdown itself:
- in minutes
- in %.
There is also difference between Low Battery Duration and Basic Low Battery Duration up to connected interface network/SNMP or basic signaling cable.
Then it needs to take into account level of battery capacity for return to normal operation. Drained batteries can't provide their primary feature = UPS for safe time and next shutdown in case of repeated outage.

As you wrote, setup needs to be tested. No one knows how fast load from connected device(s) will drain capacity of batteries (now, next year, ...).
Settings of the % is better than minutes. But Syno can provide just "Until low battery", what is for me out of safe and controlled area.

Another point:
Seems to be old story for me from 2012, that there isn't SNMP traps support in DSM. It will be great, when SNMP traps e.g. Shutdown will be received and processed by NAS in normal way as is in other devices.
I have ticket in Syno support. Waiting for an answer.
Yea I hate the fact that I can't just submit a % here instead of a fixed time..

Or I would choose something like 10% or something.
What is Synology or the UPS considering as 'low battery'?
Syno has all the necessary data, when you will check it by:

upsc ups@localhost

you will get:

so first answer from Syno support is simple (as was expected from 1st line):

My note:
we need wait 14 days for deeper level of Syno support to get answer for:
Is receiving and processing of the SNMP traps integrated in DSM? If yes how to use it?
(as you know me, there was detailed description provided for them)
I use 5 minutes to trigger safe mode, figuring that if the power hasn't restored by then, it will be out for a while. I let the UPS continue from there (until it dies) as it supports modem/router for my laptop and mobile devices that I continue to use until I cannot.
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Food for thought... Two main reasons to have a UPS... #1: to protect data and equipment from unexpected power loss or spikes - #2: to provide operational capability during a power failure.

Protection of data and equipment is usually the highest priority. And that can be accomplished safely by shutting down systems within minutes of a power failure.

For a home/hobby user vs. small business vs. enterprise, the cost/benefit and practicality of providing power during a power failure will vary considerably. But in many use cases, the cost of supporting operation during a prolonged power failure can significantly outweigh any practical benefit.

It is also useful to look at the pattern of outages in your area: frequency and duration. I previously lived in an area where power failures occurred 2-3 times per year; and lasted at least a few hours - sometimes days. So it wasn't practical to provide UPS power for the duration. I currently live in an area where failures occur more frequently; but typically last less than five minutes. So it is much more practical to provide power for the duration of the outage. I currently run 15 minutes before shutting down.

Your local power utility should be able to give you some background regarding the cause, frequency, and duration of outages in your area. Good to know...

My first UPS was an APC SMX (extended run time) series. With an extra battery pack, I was hoping it could outlast the longer power failures I was experiencing at the time. But I gave up on trying to support operations during a failure; and now use APC's SMC series to provide a safe shutdown.

Good points.

My initial reason for getting a UPS was to protect an old iMac and its external drives, that was after experiencing the fun of rebuilding a zapped drive following a power outage. So, yes, the protection of devices and data has been the main reason. But as I've predominantly worked from home for a number of years it has also been very useful to be able to work through any power outage: hence having the modem, router, and switch on UPS.

Most of the outages we get I suspect are due to the house building that's been happening but these usually are over before the UPS's get low and shutdown/safe mode gets initiated. Maybe I'll put the NAS's (and switch, and their ext. disks) safe mode back to 'until low battery' and hopefully that will give the NAS long enough for repeated events.
Last edited by a moderator:
Another thing to consider in the work-from-home scenario... Especially if outages are often hours or longer... It can be very useful to leave some capacity in the UPS for recharging electronics' batteries, safety lights, running small appliances, etc. However, we initially learned the hard way that some UPS will only power up when connected to utility power!

At my previous location, we were also plagued by high-wind and lightning related surges that would cause the UPS to kick in erratically. After a bit of research, we settled on a Zero Surge protection device; which completely resolved that issue. Their Website provides a great deal of information about the technology. For supplemental power sources such as generators or a UPS, they provide this specific information. Note that Zero Surge licenses its technology to a few other manufacturers such as Ametek/Surgex; but I'm not sure about Zero Surge's availability outside of North America.

Error in previous post... We are currently using the APC SMT series UPS (not SMC, as stated incorrectly). The SMT is a cloud-enabled UPS, using a secure portal that allows you to view the status of each UPS, receive status notifications, get firmware updates, etc.

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